The electrical resistivity of metals increases with temperature due to phonons interfering with electron movement through the metal lattice. Phonons describe the vibrational motion of atoms in the lattice which increases with temperature, causing more scattering of electrons. The electrical resistivity of semiconductors decreases with temperature because the number of charge carriers increases exponentially with temperature due to excitations across the band gap, overcoming the decrease in carrier mobility.

1. Temperature dependence of
conduction

2. • electrical resistivity of metals increases with
temperature
• electrical resistivity of semi conductors
decrease with temperature

3. Metals

4. Phonon
• It is a description of an elementary vibrational
motion in which a lattice of atoms or
molecules uniformly oscillates at a single
frequency
• It is a normal mode of vibration according to
the classical mechanics

5. • The carrier (electrons in conduction band)
concentration changes very slowly with
temperature in metals
• So, can not consider its effect

6. • Atoms at absolute zero sit locked into their
lattice sites and don't move; they are frozen in
place
• But at any temperature warmer than absolute
zero, they bounce and wiggle around, causing
them to move slightly out of their lattice sites
• Called phonons

7. • These warmer atoms can begin to choke off
the channels through the lattice and to
interfere with electrons travelling through the
channels
• The warmer they are, the more they wiggle
and the more interfere
• Effectively, they start to block electrons on
their path, causing electrons to scatter

8. • The more motion of atoms, the more
interference
• The more phonons, the more interferences
• The more interference, slower the motion of
electrons
• Slower the motion of electrons, higher the
resistance

9. Semi conductors

10. • Carrier concentration increases as temperature goes up, due to
excitations across the band gap
• s= ne2t/m* (s=conduction)
• n is proportional to exp{-Eg/2kT}
• When T increases, term exp{-Eg/2kT} increases, so “n” increases (n
= # of charge carriers)
• t inversely proportional to T (when T increase, t decrease) so, s
decreases
• Two terms, opposite actions (n & t)
• But, exponential term dominates, increasing the conduction with
temperature
• So, mainly due to the increasing charge carriers
• T = temperature
• t = term in equation

11. THANK YOU